This guy once lent Bruno Mars a jacket; now, they’re a creative dream team

In the video for Bruno Mars’ “24K Magic,” the Hawaiian pop star cruises around Las Vegas in a convertible and rides a Jet Ski through the Bellagio fountains, donning enough bling to blind unsuspecting passers-by. But Mars’ biggest baller move happened before the cameras even started rolling.

As Cameron Duddy, who co-directed the video with Mars, tells The Post, the fun began while they were in Vegas scouting locations for the video, which earned three nominations at this year’s MTV Video Music Awards.

“Bruno was at a roulette wheel and had amassed a stack of chips,” says the 31-year-old, who grew up in California. “I don’t know how much it was, but it was probably more money than I’ve ever made in my life.”

Mars invited him to bet on red or black. After three attempts, only one of their bets came in right. “Even though I lost him money, he said, ‘Here’s a little something for your trouble’ and flips me a $10,000 chip. I put it in my pocket and used it to pay off my truck that I owed on!”

Mars does have a generous streak (he recently donated $1 million to assist those affected by the water crisis in Flint, Mich.), but he also has a special place in his heart for Duddy. The two have worked together on several Mars videos, including “The Lazy Song” (2011), “Locked Out of Heaven” (2012), “Gorilla” (2013), and even the Mark Ronson and Bruno Mars collaboration “Uptown Funk” (2014). Duddy is the secret weapon who has helped realize Mars’ vision over the years.

They first met on a photo shoot when Mars was freshly signed to Atlantic Records in 2009. Duddy was filming video.

“He liked my jean jacket,” laughs Duddy. “He tried it on and then offered me $300 to buy it, even though it only cost $45 or $50. When he did the next video for ‘Just the Way You Are,’ his stylist called me up to ask if he could borrow it. I said, ‘Yes, but only if I can shoot some behind-the-scenes footage.’ ”

It was a mutually beneficial arrangement. Duddy got to develop his relationship with Mars, and Mars got to rock the jacket (he ended up wearing it for the entire video).

But Duddy now also has a pretty good side hustle playing bass guitar in his country band, Midland. The group — completed by singer Mark Wystrach and guitarist Jess Carson — formed around Duddy’s 2013 Wyoming wedding to photographer Harper Smith. Longtime pals Wystrach and Carson were Duddy’s groomsmen, and in the week leading up to Duddy’s big day, they began playing country and classic-rock covers for fun.

Cameron Duddy is Bruno Mars’s secret creative weapon.Harper Smith

Mars was encouraging of Duddy’s burgeoning band, and even flew them out to Los Angeles to work on early writing sessions. “It gave us confidence to know that someone like that, who was at the top of his game, was enjoying what we were doing,” says Duddy.

It also helped attract the attention of the music industry: Midland is now signed to Taylor Swift’s label, Big Machine.

Their first album, “On the Rocks,” is due for release next month and currently they look likely to score a No. 1 on the country charts with their debut single, “Drinkin’ Problem,” a song about the small joys of drowning your bigger sorrows with booze.

“I think people relate to it as a song about going down in flames with a middle finger in the air,” says Duddy.

With the band’s rise happening faster than anyone expected, that’s not a problem Midland has.